Battery measuring clamps are becoming increasingly important in automobile manufacture due to the increasing number of comfort-related consumers in modern motor vehicles. Due to the increasing number of comfort-related consumers, the power consumption during rest times of the vehicle is also increasing. The battery has to supply the comfort-related consumers with power even in rest times of the vehicle, which leads to a constant, if slow, discharging of the battery.
In order to allow starting of an internal combustion engine, a sufficiently high current must be available on the starter at the time of starting. This can be provided only if the battery is sufficiently charged. If, during relatively long rest times, there is a partial discharging of the battery below a minimum state of charge, reliable starting of the internal combustion engine can no longer be ensured.
In order to prevent the battery from being discharged below a minimum state of charge, battery measuring clamps are used. The battery measuring clamps measure at least a voltage drop across a measuring resistor (shunt). Based on the voltage drop, it is possible to draw conclusions about the current flow. Furthermore, using suitable evaluation means, the battery temperature and also other physical parameters of the battery can be evaluated directly on the battery measuring clamp by means of an evaluation circuit. The measured parameters can be used to draw conclusions about the state of charge of the battery. In particular, the use of the parameters current, voltage and temperature makes it possible to detect and output the charge state of the battery. Based on such an evaluation, it is possible to switch off comfort-related consumers rather than discharging the battery below a minimum state of charge.
The battery measuring clamps are usually installed directly in the pole recess on the battery pole. The values measured by the battery measuring clamp can be tapped off via a data line. However, due to a large number of different plug systems in automobile manufacture, there are problems in terms of making the data available to the on-board management system of the vehicle using an inexpensive solution. Different plug variants are necessary in order to meet different manufacturers' requirements for a data interface.